1. Field of the Invention
The present invention relates to magnetically affixed fluid pump devices, and more specifically to a submersible aquarium pump utilizing a centrifugal design that can be easily positioned by manipulating a magnetic affixing device to affect changes in current within an aquarium.
2. Description of the Related Art
To adequately care for and maintain a vibrant closed aquatic environment, several items are fundamental. Water quality, light or simulated light, and a means of providing oxygen within the closed environment are all critical. Particularly with salt or brackish water environments, the ability to provide an alterable simulated current for distribution of oxygen and food in water columns for an extended period of time within the environment is also paramount.
In nature, aquatic environments are exposed to multiple types of water motion per day, including tidal currents, wind driven wave production, and swells. This water motion not only provides the environment with oxygen, but in environments supporting reef life, water motion encourages stronger reef growth and distribution of food to sessile life forms.
Creating realistic water movement in a closed environment poses several challenges, and to that end the prior art suggests numerous ways to address this issue. Add the concern of maintaining environmental integrity and elimination of contamination, especially important in salt and brackish environments, and the applicable field of art narrows.
To ensure proper and varied water movement, any device introduced into a closed aquatic environment must necessarily be easy to move, without the necessity of reaching into the aquarium and thus risk contaminating the environment or endangering the person reaching into the tank. Aquarium pumps that rely upon brackets or suction cups for mounting the pump are limited in mobility. To increase the ease of moving such a pump within a closed system, the prior art discloses the use of a set of magnets, one being located outside the tank and one inside the tank to which the pump may be mounted to affix an aquarium pump in place.
In U.S. Pat. No. 3,481,586 to Roberts, therein is disclosed a centrifugal aquarium pump that utilizes magnetic attraction to drive the pump. In Roberts, the pump is secured in place using a bracket that extends from the exterior of the tank into the tank itself to secure the pump to the interior surface of the aquarium wall. As pointed out in Roberts, the circulation of water in an aquarium tank is important for several reasons. 
In U.S. Patent Application No. 2006/0210412 to Lawyer, et al., there is disclosed a bracketless magnetic pump. In Lawyer, an impeller is located within the aquarium and is secured in place along an interior wall of the aquarium by a magnet attracted to an opposing magnet located outside the aquarium. The impeller, in turn, is driven by magnetic force. In Lawyer, et al, the first casing and the second casing automatically come into coaxial alignment by virtue of the magnetic attraction provided by the magnetic assemblies and communicating magnetically with each other. The first casing and the second casing are prevented from rotating and held against gravity by means of at least one first friction member attached to an inner face of the first casing facing the first side 6a of the side wall of the container, and at least one second friction member attached to an outer face of the second casing facing the second side of the side wall of the container. The friction members and are made from material with a relatively high friction coefficient and preferably are formed from a resilient material. 
The device in Lawyer achieves advantages over Roberts in not relying upon brackets, which provides the ability to position the pump within the environment without risking contamination to the environment. Lawyer, however, relies upon magnetic force through the pane of the aquarium to drive the impeller, which may not provide the optimum amount of power to the unit to create a water current, as opposed to merely providing aeration. Further, the unit located outside the tank can be heavy and not able to be adequately supported by magnetic attraction alone, resulting in either the unit not remaining in the place, or necessitating the reliance on suction cups or brackets to hold the unit in place. This is not as significant an issue if the unit is being used for aeration purposes alone. However, placement of the pump is critical when trying to achieve simulated current.
In addition to placement of the unit, flow rate is also significant when attempting to achieve current production, as opposed to aeration. Any number of pumps exist in the prior art that are designed to provide aeration to a closed aquatic environment. However, to introduce a current into the environment to encourage healthy reef growth, a unit must be able to be easily moved into various positions without contaminating the environment, and must provide both adequate water intake and outflow from the unit and enough power to create a current.
Therefore, there is a need for an aquarium pump that can be magnetically mounted in place without reliance on additional support mechanisms such as brackets or suction cups, easily moved (i.e., laterally translated when mounted to aquarium wall) without the necessity of reaching into the aquarium, and capable of creating enough force to effectuate the creation of a current capable of encouraging reef growth by diffusing or dissolving oxygen into the water with no stagnant or dead spots and the provision of food throughout the aquarium, as opposed to effectuating the aeration of the environment through the introduction of larger bubbles.